---
title: "Convex React"
sidebar_label: "React"
sidebar_position: 4
description: "React client library for interacting with your Convex backend"
---

import SkipBad from "!!raw-loader!@site/../private-demos/snippets/src/reactSkipBad.tsx";
import SkipGood from "!!raw-loader!@site/../private-demos/snippets/src/reactSkipGood.tsx";

Convex React is the client library enabling your React application to interact
with your Convex backend. It allows your frontend code to:

1. Call your [queries](/functions/query-functions.mdx),
   [mutations](/functions/mutation-functions.mdx) and
   [actions](/functions/actions.mdx)
2. Upload and display files from [File Storage](/file-storage.mdx)
3. Authenticate users using [Authentication](/auth.mdx)
4. Implement full text [Search](/search.mdx) over your data

The Convex React client is open source and available on
[GitHub](https://github.com/get-convex/convex-js).

Follow the [React Quickstart](/quickstart/react.mdx) to get started with React
using [Vite](https://vitejs.dev/).

## Installation

Convex React is part of the `convex` npm package:

```
npm install convex
```

## Connecting to a backend

The [`ConvexReactClient`](/api/classes/react.ConvexReactClient) maintains a
connection to your Convex backend, and is used by the React hooks described
below to call your functions.

First you need to create an instance of the client by giving it your backend
deployment URL. See [Configuring Deployment URL](/client/react/project-setup.md)
on how to pass in the right value:

```jsx
import { ConvexProvider, ConvexReactClient } from "convex/react";

const convex = new ConvexReactClient("https://<your domain here>.convex.cloud");
```

And then you make the client available to your app by passing it in to a
[`ConvexProvider`](/api/modules/react#convexprovider) wrapping your component
tree:

```jsx
reactDOMRoot.render(
  <React.StrictMode>
    <ConvexProvider client={convex}>
      <App />
    </ConvexProvider>
  </React.StrictMode>,
);
```

## Fetching data

Your React app fetches data using the [`useQuery`](/api/modules/react#usequery)
React hook by calling your [queries](/functions/query-functions.mdx) via an
[`api`](/generated-api/api.md#api) object.

The `npx convex dev` command generates this api object for you in the
`convex/_generated/api.js` module to provide better autocompletion in JavaScript
and end-to-end type safety in
[TypeScript](/understanding/best-practices/typescript.mdx):

```tsx title="src/App.tsx"
import { useQuery } from "convex/react";
import { api } from "../convex/_generated/api";

export function App() {
  const data = useQuery(api.functions.myQuery);
  return data ?? "Loading...";
}
```

The `useQuery` hook returns `undefined` while the data is first loading and
afterwards the return value of your query.

### Query arguments

Arguments to your query follow the query name:

```tsx title="src/App.tsx"
export function App() {
  const a = "Hello world";
  const b = 4;
  const data = useQuery(api.functions.myQuery, { a, b });
  //...
}
```

### Reactivity

The `useQuery` hook makes your app automatically reactive: when the underlying
data changes in your database, your component rerenders with the new query
result.

The first time the hook is used it creates a subscription to your backend for a
given query and any arguments you pass in. When your component unmounts, the
subscription is canceled.

### Consistency

Convex React ensures that your application always renders a consistent view of
the query results based on a single state of the underlying database.

Imagine a mutation changes some data in the database, and that 2 different
`useQuery` call sites rely on this data. Your app will never render in an
inconsistent state where only one of the `useQuery` call sites reflects the new
data.

### Paginating queries

See
[Paginating within React Components](/database/pagination.mdx#paginating-within-react-components).

### Skipping queries

<Details summary="Advanced: Loading a query conditionally">

With React it can be tricky to dynamically invoke a hook, because hooks cannot
be placed inside conditionals or after early returns:

<TSAndJSSnippet
  title="src/App.tsx"
  sourceTS={SkipBad}
  sourceJS={SkipBad}
  snippet="example"
  highlightPatterns={["useQuery"]}
/>

For this reason `useQuery` can be "disabled" by passing in `"skip"` instead of
its arguments:

<TSAndJSSnippet
  title="src/App.tsx"
  sourceTS={SkipGood}
  sourceJS={SkipGood}
  highlightPatterns={["skip"]}
/>

When `"skip"` is used the `useQuery` doesn't talk to your backend at all and
returns `undefined`.

</Details>

### One-off queries

<Details summary="Advanced: Fetching a query from a callback">

Sometimes you might want to read state from the database in response to a user
action, for example to validate given input, without making any changes to the
database. In this case you can use a one-off
[`query`](/api/classes/react.ConvexReactClient#query) call, similarly to calling
mutations and actions.

The async method `query` is exposed on the `ConvexReactClient`, which you can
reference in your components via the
[`useConvex()`](/api/modules/react#useconvex) hook.

```tsx title="src/App.tsx"
import { useConvex } from "convex/react";
import { api } from "../convex/_generated/api";

export function App() {
  const convex = useConvex();
  return (
    <button
      onClick={async () => {
        console.log(await convex.query(api.functions.myQuery));
      }}
    >
      Check
    </button>
  );
}
```

</Details>

## Editing data

Your React app edits data using the
[`useMutation`](/api/modules/react#usemutation) React hook by calling your
[mutations](/functions/mutation-functions.mdx).

The `convex dev` command generates this api object for you in the
`convex/_generated/api.js` module to provide better autocompletion in JavaScript
and end-to-end type safety in
[TypeScript](/understanding/best-practices/typescript.mdx):

```tsx title="src/App.tsx"
import { useMutation } from "convex/react";
import { api } from "../convex/_generated/api";

export function App() {
  const doSomething = useMutation(api.functions.doSomething);
  return <button onClick={() => doSomething()}>Click me</button>;
}
```

The hook returns an `async` function which performs the call to the mutation.

### Mutation arguments

Arguments to your mutation are passed to the `async` function returned from
`useMutation`:

```tsx title="src/App.tsx"
export function App() {
  const a = "Hello world";
  const b = 4;
  const doSomething = useMutation(api.functions.doSomething);
  return <button onClick={() => doSomething({ a, b })}>Click me</button>;
}
```

### Mutation response and error handling

The mutation can optionally return a value or throw errors, which you can
[`await`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await):

```tsx title="src/App.tsx"
export function App() {
  const doSomething = useMutation(api.functions.doSomething);
  const onClick = () => {
    async function callBackend() {
      try {
        const result = await doSomething();
      } catch (error) {
        console.error(error);
      }
      console.log(result);
    }
    void callBackend();
  };
  return <button onClick={onClick}>Click me</button>;
}
```

Or handle as a
[`Promise`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise):

```tsx title="src/App.tsx"
export function App() {
  const doSomething = useMutation(api.functions.doSomething);
  const onClick = () => {
    doSomething()
      .catch((error) => {
        console.error(error);
      })
      .then((result) => {
        console.log(result);
      });
  };
  return <button onClick={onClick}>Click me</button>;
}
```

Learn more about [Error Handling](/functions/error-handling/error-handling.mdx)
in functions.

### Retries

Convex React automatically retries mutations until they are confirmed to have
been written to the database. The Convex backend ensures that despite multiple
retries, every mutation call only executes once.

Additionally, Convex React will warn users if they try to close their browser
tab while there are outstanding mutations. This means that when you call a
Convex mutation, you can be sure that the user's edits won't be lost.

### Optimistic updates

Convex queries are fully reactive, so all query results will be automatically
updated after a mutation. Sometimes you may want to update the UI before the
mutation changes propagate back to the client. To accomplish this, you can
configure an _optimistic update_ to execute as part of your mutation.

Optimistic updates are temporary, local changes to your query results which are
used to make your app more responsive.

See [Optimistic Updates](/client/react/optimistic-updates.mdx) on how to
configure them.

## Calling third-party APIs

Your React app can read data, call third-party services, and write data with a
single backend call using the [`useAction`](/api/modules/react#useaction) React
hook by calling your [actions](/functions/actions.mdx).

Like `useQuery` and `useMutation`, this hook is used with the `api` object
generated for you in the `convex/_generated/api.js` module to provide better
autocompletion in JavaScript and end-to-end type safety in
[TypeScript](/understanding/best-practices/typescript.mdx):

```tsx title="src/App.tsx"
import { useAction } from "convex/react";
import { api } from "../convex/_generated/api";

export function App() {
  const doSomeAction = useAction(api.functions.doSomeAction);
  return <button onClick={() => doSomeAction()}>Click me</button>;
}
```

The hook returns an `async` function which performs the call to the action.

### Action arguments

Action arguments work exactly the same as
[mutation arguments](#mutation-arguments).

### Action response and error handling

Action response and error handling work exactly the same as
[mutation response and error handling](#mutation-response-and-error-handling).

Actions do not support automatic retries or optimistic updates.

## Under the hood

The [`ConvexReactClient`](/api/classes/react.ConvexReactClient) connects to your
Convex deployment by creating a
[`WebSocket`](https://developer.mozilla.org/en-US/docs/Web/API/WebSocket). The
WebSocket provides a 2-way communication channel over TCP. This allows Convex to
push new query results reactively to the client without the client needing to
poll for updates.

If the internet connection drops, the client will handle reconnecting and
re-establishing the Convex session automatically.
